


congratulations

by TrasBen



Category: Undertale (Video Game)
Genre: Alternate Universe - Underfell (Undertale), But so is Sans so, Fluff, Grillby is an ass, He's 21 now, It's Papy's birthday, Lingerie, M/M, Mildly suggestive at some parts, Pregnancy, Skeleton Pregnancy (Undertale), Tooth-Rotting Fluff, ahhh even more fluff now, every new chapter brings more fluff, mostly just, we're reaching critical levels of fluff
Language: English
Status: Completed
Published: 2020-07-21
Updated: 2020-12-29
Packaged: 2021-03-05 00:27:25
Rating: Teen And Up Audiences
Warnings: No Archive Warnings Apply
Chapters: 3
Words: 11,728
Publisher: archiveofourown.org
Story URL: https://archiveofourown.org/works/25425376
Author URL: https://archiveofourown.org/users/TrasBen/pseuds/TrasBen
Summary: It's Papyrus' twenty first birthday and Sans wants things to be perfect.
Relationships: Grillby/Sans (Undertale), Papyrus & Sans (Undertale)
Comments: 32
Kudos: 92





	1. Chapter 1

**Author's Note:**

> heads up: there's a little bit of talk of what-if scenarios for failed pregnancy/miscarriage! not graphic or super prevalent but if you're sensitive to that then here's your warning.

Sans feels… happy.

The fact itself is almost enough to send him spiraling into anxiety. It’s one thing after the other in the Underground, and he’s no stranger to this. Sans has fought for a good deal of his life to keep himself and his brother safe, so to feel so… content… is surreal.

At the back of his mind, Sans can’t stop running through possible scenarios where this happiness will come to bite him in the bony butt or obsessing over whether or not he’s forgetting anything. But at the _front_ of his mind, Sans is browsing through Grillby’s extensive collection of alcohol.

It feels so hedonistic to be surrounded by expensive liquor, casually looking, as though he’s window shopping. For any other monster this would be a deadly endeavor; Grillby doesn’t take thieves lightly, and no one is allowed in the back where he keeps the expensive drinks.

But Grillby is at Sans’ back, closing up the bar for the night. Sans has his permission to be here and to choose any drink he wants. He’s safe, taken care of. 

Again, it doesn’t feel quite real.

But Sans has never been one to look a gift horse in the mouth.

He must have been looking at the _drinks_ for too long, though, because warm arms suddenly wrap around him from behind. If Sans weren’t familiar with the spark of magic or the shape of the body behind him, he would have reacted swiftly and defensively.

As it is, Sans knows the flaming bartender _quite_ intimately, so he leans back into the arms and continues looking ahead.

“finished closin’ up?” Sans asks idly, stroking the length of the arms wrapped around his middle.

“... _no._ ” The whispery, low voice behind him replies. Sans frowns and tries to turn around, but Grillby’s arms hold him firmly in place. “ _... there’s still one… picky…. indecisive… customer i’m waiting for.”_

Sans almost responds seriously before he realizes that it’s _him_ Grillby’s talking about. A small gasp alerts the flame monster to the realization, and Grillby laughs as his hold on Sans loosens. The small skeleton uses the opportunity to turn around and smack his boyfriend on the shoulder.

But Sans can’t help joining Grillby in his laughter. He still slaps him lightly a couple more times, though. Just so he knows that Sans won’t tolerate that sort of talk.

One weak slap to Grillby’s cheek is all the elemental needs to grab up one of Sans’ hands and hold it there, to his face. Sans blushes as it forces his eye lights to meet Grillby’s own. Grillby, the sentimental bastard, is crouching down to be at Sans’ level since he’s ridiculously short compared to the elemental.

The flames that make up Grillby’s body are flickering blues and purples, but his eyes are magenta. It’s one of Sans’ favorite color, so rare in the dreary Underground. No natural flames will ever be as impressive or graceful as Grillby’s.

His eyes are usually hidden behind a pair of thick sunglasses, but much like his gruff and uncaring persona, Grillby sheds them in the safety of the bar after hours. It’s nice, almost sickeningly sweet.

If Sans were any less tired and lazy, he might have put up a wall to protect himself from the obvious displays of affection. But Grillby had long ago, _heh,_ _melted_ away all those layers. He’s stripped Sans down to more than just his bare bones and _burned_ away all hesitation. Throughout his childhood, Sans had rarely felt safe. But in Grillby’s arms, the feeling is natural, almost.

He can’t stop himself from leaning forwards to plant a kiss on the seam where Grillby’s mouth manifests when he grins widely enough or laughs or whispers loving things into Sans’ acoustic meatus.

Neither skeletons nor flame elementals have lips, but as they brush their faces together, Sans can feel sparks all the same. He almost rises to his tippy-toes with a sigh of contentment.

He’s _happy._

Which is why his grin nearly splits his skull when he whispers up against Grillby’s mouth. “bastard.” Sans accuses. It’s soft. He feels soft. He’d never thought that he’d be _soft._

_“... dipshit…”_ Grillby returns fondly, arms wrapping around Sans’ middle once again. _“did you… pick something out?”_

Sans pulls back so he can look at the wall of liquor again. His grin falls to a tight line as he thinks. “i dunno. want it to be special for paps, but none of this seems… _him…_ y’know?”

Grillby hums as he returns to his full height. He walks around Sans to stand in front of another section on the wall. “ _... have you looked at…. the wines?”_

Sans makes a sound like he’s clicking his tongue and saunters over. He gives the bottles an appraising look. “yeah… yeah…” He replies, “this is more of paps’ speed. got anything sweet?”

Grillby doesn’t say anything, just brushes his fingers along a few bottles before he pulls one off the shelf and hands it to Sans. 

“ _moscato d’asti…. it’s good for beginners.”_

Sans pops the cork off with one of his sharp phalanges and takes a whiff. He blinks up at Grillby and whistles.

The flame monster in question grins the magenta flames behind the seam of his mouth exposing itself. “ _low in alcohol… it’s a dessert wine._ ”

Sans nods along and corks the bottle up again. “prolly a good introduction for him then. paps has always had a sweet tooth…” He grins fondly and tucks the bottle under his arm. 

“wish i could take a quick sample…” Sans sighs heavily a moment later. The wine had smelled really nice and he’d be lying if he said that he didn’t have his own penchant for sweets, namely chocolate.

_"... papyrus…. is going to question why you don’t._ ” Grillby states. Sans cringes because he knows it’s true. His free hand goes to brush under his ribs, where there should be an empty cavity backed by vertebrae. The cushy feel of ecto flesh greets him.

“i’ll tell him soon.” Sans insists.

“ _why not tonight?”_ Grillby counters.

The stout skeleton looks up at his boyfriend and sighs gruffly. Soon, but not tonight. Tonight is reserved for Papyrus only.

“it’s his birthday, grillbs. today is paps’ day, i don’t wanna take away from that. we don’t even...” Sans sucks in a sharp breath and strokes over his stomach again, “it’s too early to know if it’ll stick.” He adds quietly.

It’d only been a few days ago that the ecto-flesh had manifested and Sans had realized that the world just got a whole lot scarier. Sans had never before given any thought to… this sort of thing… but he found that the surprise wasn’t unwelcome. It’s a future Sans never imagined he’d be allowed to have, but now that it’s within his grasp, he won’t let anything make him let go.

Grillby pulls Sans into his side and rubs the top of his skull. “ _it will, … i’m sure._ ” Silence reigns shortly before Grillby continues, hesitantly, as if he’s worried Sans will strike him down for saying the wrong thing. “ _do you think… he’ll be happy to learn… that he’s going to be an uncle?”_

Sans chuckles, shoulders bouncing. “he’ll probably start screechin’ about how he’ll be the best uncle in the whole underground.” 

Grillby returns the laugh and leads Sans to the main area of the bar, where there’s a table in the center of the room, all others pushed out of the way. On it are some plates and cutlery, not yet arranged.

Sans is too busy admiring the candles Grillby’s set out to notice when the gentle laughter turns into a snicker and he feels a sharp slap across his coccyx. He yelps and nearly drops the bottle of wine he’s _just_ picked out.

Whirling around, Sans jabs a finger into Grillby’s midriff and huffs.

“three days, you lit fart.” He tells the taller scathingly.

Grillby’s jagged smirk grows as he crosses his arms over his chest. He almost looks like how he does on the job, confident, strong. Sans _does not_ blush because he _does not_ think it’s hot. “... _i don’t know… what you mean..”_

“the hell you don’t! i should make it a week that your dick’s gonna be dryer than dust in hotland!” Sans threatens. Grillby’s smug look doesn’t falter. Sans keeps his metaphorical hackles raised, although he knows it’s an empty threat.

“... _like you can keep your legs closed for that long.”_ Sans’ eye sockets widen as his eye lights constrict. Fucking asshole!

He voices his thoughts with a growl and turns back to the table stiffly.

“ _rather eloquent for a slut.”_ Grillby responds simply.

Sans flips him off, “yeah yeah, go make yourself useful for once in your life and get back in the kitchen.”

“ _very well._ ” But Sans doesn’t hear footsteps retreating behind the bar. Instead, he nearly _shrieks_ when there’s another sharp slap to his ass.

“fuck you! _”_ He doesn’t otherwise argue besides flipping the bird once again over his shoulder, since Papyrus will be at the bar soon. Sans will just have to remember to get back at Grillby later for being a total ass. Finally, he hears Grillby leave.

Sans lets out a rough breath through his nasal cavity and begins to set the table. Thankfully Grillby has already folded the napkins in that fancy triangle-way because Sans doesn’t know how to fold anything other than shirts and even those end up looking lumpy.

When the table’s all pretty, Sans hears a knock at the door. He looks suspiciously at the figure through the foggy glass and sighs in relief when he sees Papyrus’ tall silhouette. Sans hurries over to the door and lets Papyrus in.

His brother is just as Sans had seen him this morning before their sentry duty: tall, imposing, somehow looking fresh off the cover of a Mettaton Brand magazine despite having just worked a ten hour shift.

He ducks his skull politely as he enters the bar, looking around with only a slight amount of disgust.

“happy birthday, boss.” Sans greets, shutting and locking the door behind his brother.

“SO YOU’VE SAID ONLY TWENTY TIMES TODAY.” Papyrus replies sarcastically. His grin, composed of serrated fangs, curls up at the edges, though. He’s always been a sucker for praise and Sans has never left him bereft of it.

“‘s’not every day you turn the big two-one. congrats for not dying or whatever, fuckwad.” Sans’ own dopey grin and teasing tone gives away his true feelings. He’s proud, immeasurably so. Back when Sans was just a kid himself, trying to make it on the streets of New Home, he could’ve never imagined this outcome.

A secure house, a caring partner… Papyrus, all grown up and strong. And… a tiny babybones on the way. Hopefully.

“TRULY, I FEEL THE LOVE. WHERE IS YOUR BEAU?” Papyrus looks around the empty bar. It’s darker without Grillby out in the main area, since he’s the primary source of light at the bar.

“pfft, where he belongs” Sans playfully scoffs and leads his brother to the table, even pulling out a seat for him and everything, much to Papyrus’ surprise. Sans supposes it must be quite the shock to see his lazy brother going the extra mile. Or even the full mile, really. 

It’s just then that Grillby exits the kitchen, three serving trays in his hands and balanced on his arm. They’ve got one of those fancy covers and Sans melts a little because this is important to him and he’s glad that Grillby’s taking it so seriously. 

Papyrus is almost like his own kid, in a way. For a long, long, time, he’d been his only reason for living, too.

_“what sans means... is that i’ve been slaving over your meal._ ” Grillby explains. _“don’t worry,_ dear _,”_ he addresses Sans this time, _“i’ve made sure to spit in yours…. per preference.”_

Papyrus’ expression curls in mild revulsion. “EUGH.”

Sans bursts into laughter and sits in his own chair sloppily. “sleep with one eye open, _dear_.”

“ _it’s hard not to… with how loud you snore._ ”

“you think it’s hot.” Sans leers with a lasvacious brow bone wiggle.

Before they can torture his ear holes any longer, Papyrus interjects. “THAT’S MORE THAN I’VE EVER NEEDED TO KNOW. THANKS, NOW STOP.”

Sans almost wants to coo at his brother’s tone, the same as he used to sound when Sans would spout puns and Papyrus would groan. He hasn’t reacted to one of Sans’ jokes like that since he was still in stripes, though. This is great. Sans is nearly glowing with happiness, not that anybody who doesn’t know him well could tell.

“ _it’s true… though…_ ” Grillby’s near-sinister look grows as he drags out the joke even further. “ _the desire to shut you up is strong… even in your sleep.”_

Sans winks. “yeah, shut me up with your d-”

“YOU TWO WERE MADE FOR EACH OTHER.” Papyrus comments, but when he says it, it doesn’t sound so much like a compliment. The thought is confirmed when Papyrus says, “HORRIBLE AND VULGAR. A MATCH MADE BY THE STARS.”

Sans tsks playfully, “what, a fella can’t say di-”

“COMIC SANS…” The warning tone isn’t enough for the older brother’s smile to fall.

“alright, alright…” Sans can hardly hide the way his hands twitch with mirth, “i won’t be so _vulgar,_ fine.”

“THANK YOU.” Papyrus sniffs. Too soon, of course, because Sans has never once held back when it comes to being any sort of crude and Papyrus should know this.

“i’ll use the right term. penis.” Sans says.

He manages to keep his face straight for long enough to fool the others at the table. As soon as the full sentence comes out of his mouth, Grillby can’t hide his loud, sudden laughter. The flame elemental bangs his fist on the table, rattling the cutlery as he bends over the table. Sans can’t hold back his own snickers for much longer, and is soon in a similar state as the elemental.

Papyrus is less amused. “HOW TERRIBLY TRAGIC THAT THE DAY I CAME INTO THE WORLD IS THE DAY I’LL HAVE TO TAKE MY ONLY FAMILY MEMBER OUT OF IT.”

“d...don’t be like that, boss…” Sans wipes a legitimate tear out of his eye socket, “i’m… i’m just _ribbin’_ ya! hah!”

All at once, Papyrus’ bravado seems to deflate as he rolls his eye lights and sits back in his chair. He looks like a bored teenager. Hell, it seems like he _was_ a bored teenager just yesterday. But he’s an adult now, old enough to drink and get arrested and do whatever the fuck he wants.

The laughter tapers off after a moment. Sans lets out a heavy sigh while Grillby leasieruly puts his arm over the back of Sans’ chair. The two of them are seated across from Papyrus, like this is the least professional business meeting ever.

“ _... happy birthday…_ ” Grillby says when he’s calmed down.

There’s a slight tinge of red on Papyrus’ skull when he accepts the congratulations. “HONESTLY…” He grumbles, embarrassed. “I’D PREFER TO EARN PRAISE FOR DOING SOMETHING MORE IMPRESSIVE THAN LIVING SLIGHTLY PAST MAJORITY.”

Grillby shrugs. “ _some get… half as many._ ”

The mood of the room is somber for a minute. Sans remembers all the birthdays before this one. Back before they had a house and Papyrus’ gift was Sans taking him from their dingy corner in New Home out to Waterfall to look at the ‘stars’.

“yeah, well, this is a special day.” Sans says, if only to convince himself of cheer. “today my baby bro gets t’ join the big kids and have some real drinks.” If one could really call whatever Grillby had suggested a _real_ drink. Sans had seen the alcohol content.

It seems as though Papyrus just then notices that besides the yet to be uncovered dishes, there’s a wine glass in front of his and Grillby’s plate. He looks suspiciously at Sans’ setting but finds nothing other than a mustard bottle sitting beside it, looking out of place among the fancy dishes and napkins.

“ALRIGHT THEN.” Papyrus concedes, “LET’S EAT.”

Finally, the three uncover their dishes to find that Grillby’s made a plate of spaghetti and some salad. Sans nearly gags when he sees the green bits on his plate but refrains. It’s likely for Papyrus’ benefit. All for Papyrus, it’s his birthday… ugh.

Other than that Sans owes Grillby a pat on the back. Papyrus loves pasta, but hates it when others make lasagna. Sans knows it’s because he gets jealous. He pretends to buy that Papyrus believes all other lasagna is inferior.

As they eat, the conversation flows easily, and so does the wine. Grillby doesn’t seem to have much, but Papyrus has certainly found something he _likes._ Sans can’t hide an amused smile when his younger brother goes to pour himself another _half_ glass like he hasn’t had nearly _half_ the bottle. If skeletons had a blood stream he might be in danger.

Luckily, his body is only absorbing the fermented magic and it’s making him a little loopy. It’s also a good thing that Sans and Grillby are here to keep watch.

“SANS… SANS…” Papyrus’ voice is a little feint, but it’s nothing terrible. He’s got a good control of himself, although that might just be that the alcohol content is relatively low.

Sans grunts in acknowledgement. He’s polished off his pasta, but the greenery still looms before him. Stars, he can’t be picky. He grew up eating literal garbage and rotted food. But veggies had always been his least favorite… he’d often passed them over to Papyrus who’d liked them just fine.

Maybe that’s why he’s almost seven feet tall and Sans hasn’t even cleared five feet himself.

“ARE YOU… ALRIGHT?” That has Sans snapping his skull up. 

“uh… yeah?” He replies. “just fine, boss.”

“YOU HAVEN’T HAD ANYTHING TO DRINK.” Papyrus notes. He almost sounds worried. Heh. If someone told Sans a year ago that Papyrus would be worried over him _not_ drinking, he’d have laughed in their face.

“heh, whaddya mean, boss? i got my mustard.” To demonstrate, Sans takes up his condiment bottle, shakes it around a little, and takes a long gulp.

Papyrus does an almost-scowl that could be stern if the concern wasn’t showing through. “YOU _KNOW_ THAT’S NOT WHAT I MEAN.”

“uhhhh….”

Before Sans can explain, Grillby pipes up. “... _that would not be wise… considering… his condition._ ”

Papyrus’ brow bones shoot upwards while Sans groans and punches Grillby in the shoulder, a little harder than when he’d helped him with the wine earlier. He also gives a much meaner glare. Fucking hell he _told_ Grillby he didn’t want to talk about it tonight… 

Predictably, Grillby’s vague answer only incites more worry in his brother.

“WHAT DOES THAT MEAN, SANS?” Papyrus asks, looking to Sans. When Sans cringes and shys away, he turns a demanding eye light on Grillby. “WHAT DOES THAT MEAN? IS HE SICK?”

As if he couldn’t fuck up anymore, Grillby decides to take it a step further. He dances around the answer while still providing more information than Sans had really wanted to him. Granted the wanted amount of information was _zilch_.

“ _he is… more fragile._ ”

“bitchin’ _stars!_ ” Sans exclaims, “shut your dumbass mouth up!” Rather childishly, he turns in his seat to kick at Grillby as well as land a few more mean slaps. There’s no intent to harm, but he hopes it stings anyways.

Grillby easily bats him away and for one of the first times Sans really, _really_ dislikes Grillby for a moment.

“... SANS…” Stars damn it. _There’s_ the voice. The same one Papyrus had gotten when Sans had almost fallen down, back when his HP had trickled down to nearly nothing. Not even LV had brought him back up and stars know he’s gotten plenty of that in his fight for survival.

Sans can’t lie or dodge the truth when Papyrus sounds like that, especially when the look he’s leveling at his older brother is so _earnest._

He runs a hand over his bare skull and sighs as he falls back into his chair, sinking in on himself and squirming a little.

“‘m’prgn’nt.” He mumbles into the collar of his sweater.

“WHAT?”

“‘m’ _prgn’nt._ ” Sans tries again, only a little bit louder, still avoiding eye contact.

“SANS I CANNOT UNDERSTAND YOU AND UNLESS YOU WANT ME TO ADMIT YOU TO DOCTOR ALPHYS’ LABS YOU MIGHT AS WELL - “

“i’m fuckin’ _pregnant_ , delta, paps!” Sans bursts out, face red.

You couldn’t even have cut the tension in the air with one of Grillby’s wickedly sharp knives, it was so thick.

Papyrus’ jaw almost, quite literally, fell onto the table.

“... maybe.” Sans adds belatedly. Because there’s still no SOUL. it’s just a conglomerate of his and Grillby’s magic doing it’s best to form one. “it’s still _too early_ to see if it’s gonna stick.” He says with a pointed look at his boyfriend.

For all the pain he’s caused Sans, the flaming bastard doesn’t do more than roll his annoying magenta eyes and flick Sans on the forehead. " _... it will._ ” He insists.

Sans growls and swats him away. See how much the bastard feels like rolling his eyes when Sans ‘ _keeps his legs shut’_ for the next week.

“YOU… YOU…” Papyrus stares at his still half-full glass of wine with an indescribable expression, then back up to Sans. Like this entire ordeal could be blamed on the alcohol. Sans waits for the backlash. For Papyrus to scold him for thinking he could bring up _another_ child in this fucked up world. But it doesn’t come.

Instead, small red beads of liquid appear in the corner of Papyrus’ eye sockets. Sans gets to his feet, alarmed. Grillby makes an almost regretful hissing noise. 

_oh, so_ now _you’re sorry?_

“I’M GOING TO BE… I’M GOING TO BE…” Sans hopes the sudden influx of magic to Papyrus’ face doesn’t mean he’s going to be _sick_ , but it _is_ his first time drinking and he’s just had quite the surprise put on his shoulders

The little beads fall as Papyrus finally spits out, “I’M GOING TO BE AN UNCLE??”

The tension in the room breaks like it’s been shattered. Sans heaves out a sigh of relief while Grillby smacks Sans’ back as if to say, _i told you so_.

“... hopefully.” Sans replies softly.

Papyrus nods and wipes at the beads of liquid that most definitely are _not_ tears. “YES. HOPEFULLY. CAN I SEE THEM?”

Sans feels his own magic rushing to his skull as he sputters and holds his arms over his middle. “th… there isn’t even a SOUL yet!” But Sans still sits back in his chair, pushes it out a little and lifts his shirt ever so slightly with a slight nod to Papyrus. “... c’mere.”

Papyrus _stumbles_ out of his seat to come and put his hands on the glowing red ecto-flesh where hopefully a SOUL would soon appear. Perhaps those drinks had had a greater effect on his younger brother than Sans realized.

The tall skeleton poked gently at Sans’ stomach for a bit before returning to his seat. “... CONGRATULATIONS.”

Sans’ face twists up.

Dammit. This is what he’d wanted to avoid. It’s _Papyrus’_ day. He shouldn’t be congratulating Sans for being stuffed with enough magic to possibly create a SOUL. It’d been an accident, anyways. Not that he doesn't hope, well…

“don’t say that…” Sans says firmly.

Papyrus takes it the wrong way. “OH. DO YOU NOT…?”

“i _want_ it!” Sans corrects quickly. He curses quietly. “i just… today’s about you, boss. it’s your special day. don’t go congratulating _me_.”

“I DON’T BELIEVE YOU.” Finally, Papyrus’ scolding tone comes back. “WE’VE BEEN ALONE FOR SO LONG AND NOW…” He takes a quick pause to rub at his eye sockets again, “AND NOW OUR FAMILY IS GROWING… I DON’T UNDERSTAND HOW THAT ISN’T A GIFT ALL ON IT’S OWN.”

_“i told you.”_ Grillby voices smugly.

But Sans isn’t quite convinced. “boss… you do know you can’t _keep_ the baby, right?”

Papyrus uses a rather mocking rendition of Sans’ baritone as he repeats what he’s just said, “ _YOU DO KNOW YOU CAN’T KEEP THE BABY - “_ Then cuts himself off with a tremendous sigh, “OF COURSE I KNOW THAT. WHAT DO YOU TAKE ME FOR? AN IDIOT?”

Grillby cackles at Sans’ dumbstruck look and pats him on the back a few more times.

“WELL THEN.” Papyrus continues as if he hadn’t just _mocked_ Sans. “WHAT ARE MY OTHER GIFTS? IT _IS_ MY BIRTHDAY AND I’VE JUST RECEIVED EXCELLENT NEWS.”

Sans shakes himself out of the stupor and has a small laugh of his own. What had he thought? That Papyrus would tell him it was unacceptable for Sans to be pregnant? That he was devastated at the prospect of being an uncle?

“it’s in the back, i’ll go get it.” He tells his brother, striding behind the counter. To Sans’ surprise, Grillby follows.

“what’s up?”

“ _... you’ll see…_ ”

Sans snorts, _if that ain’t ominous as fuck._

He grabs a small box, all wrapped up in shiny wrapping paper with a bow on top, while Grillby gets something Sans didn’t even know he had. It looks like a fairly large stick wrapped up in cloth. He gives a questioning look to his boyfriend, but Grillby offers no explanation.

Sans also makes sure to grab the cake he’d gotten from the fridge. He’s careful with it since he’d gotten it from Muffet and he’d hate to drop a cake that cost more than his mortgage. It’s strawberry mousse, Papyrus’ favorite.

Grillby’s already back out at the table by the time Sans gets back, the stick in his lap. Sans sets the cake on the table, which already has a whole twenty one decorative candles stuck in it. It’s cheesy, but Sans will keep sticking candles onto cakes until Papyrus is over three hundred and then some.

Useful for one thing, Grillby uses his magic to light the candles and dims his flames so the room darkens.

“happy birthday, boss.” Sans says for the twenty-second time that day.

Then, he sings that stupid little birthday song that Papyrus used to adore as a kid. Papyrus flushes, likely embarrassed for the tradition, but Grillby doesn’t laugh. He doesn’t sing either, but Sans can hear the quiet humming coming from his direction.

_“happy birthday to you,_

_happy birthday to_ you _,_

_happy_ birthday _dear_ paaa-pyyy,

_happy birthday to you ~ “_

Sans claps at the end and Grillby joins in reluctantly after Sans elbows him in the side.

“make a wish.” Sans encourages. _That_ almost makes Grillby laugh but he masks it as a quiet cough when Sans elbows him again, _much harder._

Papyrus closes his sockets in concentration and blows out the candles. Soon after, Grillby cuts the cake and when everybody has a slice, Sans hands over the pretty box. “here ya go, boss.”

Trying to cover up his eagerness, Papyrus picks at the wrapping until he’s left with a simple box with a spider insignia on it. Sans had not only gotten the cake from Muffet, but another surprise, as well.

He opens it tentatively to find a bundle of red fabric inside. Papyrus looks up at Sans with shock, then pulls his favorite red scarf out of the box and rubs the material between his still gloved phalanges.

“THIS IS - “ Papyrus chokes. About a month ago, his scarf had been torn to near tatters during a battle with some thugs in Waterfall. It’d been covered in grime, too, and nearly impossible to fix. Papyrus had worn it since his childhood and had been devastated to declare it beyond saving.

But Sans had collected it up and sent it to the most talented tailor in the Underground. And now it’s good as new.

Papyrus slips the scarf on and winds it around his cervical vertebrae. “THANK YOU.” 

“no problem.” Sans replies.

It’s then that Grillby sets the cloth-covered stick on the table. No finesse. He nods to Papyrus, who looks at it with suspicion.

“IS THAT… FOR ME?” Papyrus inquires.

Grillby nods.

Papyrus picks the stick up and unwraps it from the cloth. Inside is an ornate sheath. A sheath that looks suspiciously similar to the type that holds swords…

The tall skelton slips the handle out and sure enough, there’s a sword inside.

Sans looks over at Grillby with wide eye lights. “you gave him a _sword?_ ”

Grillby shrugs, “ _it was… tradition… during the war. to give generals and captains ornate swords... symbolism.”_

Papyrus sheathes the sword once again and looks down at the beautiful outside. “I LIKE IT. THANK YOU.” He says simply. Grillby nods.

“you better not give our baby a sword for their birthday.” To Sans, it honestly sounds like a good way to have their kid’s arm accidentally chopped off.

“ _... of course not._ ” Grillby reassures, _“they will first need to master… their magic.”_

Sans contemplates hitting his boyfriend again but figures that’s too much and his arms are kind of sore from what he’s already done. Not that Grillby had probably felt a thing.

“alright.” He says, “alright. let’s just eat our cake and clean up.”

It’s not that simple, though. Because Papyrus apparently likes the taste of the wine a whole lot more when it’s paired with cake and before he knows what’s happened, the entire bottle is empty and Papyrus is slumped over the table.

“oh jeez.” Sans sighs. “can you get this cleaned up? i’ll take paps upstairs.”

_"... i see how it is._ ” Grillby teases, “ _first i’m your chef and now i’m your maid?... you better be planning on making this up to me.”_

It’s all in jest - or, at least, Sans thinks it is, but he nuzzles Grillby’s cheek with his own anyways. “heh, thanks. you didn’t have to get paps a gift… i’d let you fuck me anyways.”

_“he is… family._ ” 

Sans returns a flick on Grillby’s forehead from earlier for his sappiness. “oh? that mean i don’t have to... what did you say… _spread my legs_ anymore?”

Grillby makes a playful growl and pulls Sans back into his lap for a small grind. “ _you still owe me… for your tab._ ”

The small skeleton snorts as he slips off of his boyfriend’s lap. “yeah? welp, guess i have to, then. what else is a handsome bastard like me gonna do?” Sans fakes a swoon as he rounds the table to gather his lanky brother into his arms.

They make an absurd sight: Sans, not even five feet tall, carrying his giant of a brother like a child who’d fallen asleep in the car. 

“ _don’t strain yourself._ ” Grillby reminds Sans.

“yada yada,” Sans replies cheekily, “i got gravity magic doing most of the work for me anyways.”

He can see Grillby shaking his head in amusement before Sans starts to lumber up the stairs with Papyrus in tow. It reminds him of the good old days, when they’d first gotten the house and Papyrus would often train to exhaustion. Sans had always been there to pick him up and tuck him into bed. And he still is.

But instead of his bed, he’s tucking Papyrus in on Grillby’s couch in the apartment above the bar. It’s got a small kitchen jammed in next to a living room and a door that leads to the one bedroom. Off of the bedroom is a bathroom and that’s it.

Grillby’s couch is comfortable though. Sans lays his brother down gently and finds a nearby blanket to start tucking. Once Papyrus is secure and comfortable, Sans brushes his teeth along his forehead in a skeleton kiss and sighs.

“night, pappers.”

…

“ _you’re sweet._ ”

Sans whips around to see Grillby at the entrance of the apartment, leaning up against the doorway and smirking.

“am not.” Sans growls, like he has any sort of reputation around Grillby. “try smart, handsome, _sexy…_ ”

Grillby stalks inside, shutting the door behind him. He advances upon Sans like a predator. Against what he knows, Sans backs up a little.

“ _witty, strong… absolutely stunning._ ”

Magic rushes to Sans’ skull and he pushes Grillby away when the elemental goes for a hug. “shuddup.” He grimaces, “it’s not funny when you do it.”

“ _i’m not joking._ ”

Grillby crouches down to kiss Sans and Sans lets it happen. Might as well. He’s tired as fuck. But when Grillby’s hands start to roam, he knows he’s got to shut it down.

When they part, Sans voices his complaints. “not now,” he tells Grillby. “my feet hurt and i’m fuckin’ exhausted.”

“ _you’re not even showing yet._ ”

“It’s from running around all damn day trying to get the shit for paps.” Sans elaborates, leaning into Grillby. Damn. He’s so warm it’d be easy to fall asleep right here…

“... _alright._ ”

Sans yelps as he’s lifted straight off his feet into Grillby’s arms. He thinks about struggling but decides against it.

Grillby carries Sans to his bedroom, where he sets him down on the bed gently. Sans sighs gratefully and snuggles into the blankets.

“ _don’t fall asleep just yet, dipshit._ ” Grillby tells him. 

Sans groans and kicks his legs a little. “that’s like asking good ol’ ass-gore for mercy, y’know?”

His desire to sleep is halted by Grillby setting a box on the foot of the bed. Sans quirks a brow questioningly.

Just like on Papyrus’ gift, this box has Muffet’s business logo on it.

“wazzat?”

Grillby grins. “ _you didn’t think… papyrus would be the only one getting… a gift today, did you?_ ”

Tiredly, Sans shuffles to the end of the bed and throws the top off of the box. Inside is a silken looking purple nightgown in a suspiciously similar shade to Grillby’s flames. He throws a deadpan look up at his boyfriend. “i’m not letting you fuck me while my baby bro’s drunk-sleeping in the next room.”

_"... just try it on?_ ”

Sans stares at the nightgown. He sighs. More comfortable than his sweater, jacket, and shorts, right? “i’m tired, though…” Sans argues half-assedly.

It’s almost like Grillby had been waiting for that argument, though, because his grin doesn’t falter as he comes forward, putting a knee on the bed to loom over Sans. “ _let me help._ ”

…

“... no sex.” Sans says.

“ _no sex._ ” Grillby confirms.

The small skeleton lays back and lets Grillby undress him slowly, and when he’s bare, the light from Grillby’s flames reflecting off his ecto-flesh, Grillby slips the gown on over Sans head and guides his arms through the thin straps. It _is_ comfortable.

Sans watches through bleary sockets as Grillby removes his own restrictive clothing and joins him on the bed. But Grillby doesn’t lie beside him. Instead, he strokes one of Sans’ legs and moves it until he’s holding it in his lap.

The skeleton narrows his sockets. “no sex.” He reminds the other.

Grillby lifts Sans’ foot to his face and confirms once again, _“no sex.”_

There's a gentle brushing of flames against Sans’ foot before Grillby lowers it back to his lap and starts kneading at the magical force keeping his foot bones together. Sans makes a surprised groan.

_That felt good._

“what’re you doin’?” Sans asks suspiciously. He’s still not sure this won’t lead to sex.

_“you said your feet hurt._ ” Grillby answers.

_so it’s a massage._ Grillby’s pretty good at it. Small sighs and groans escape Sans as Grillby lavishes attention on him, his sockets slipping further and further down until Grillby slips under the covers and takes Sans with him so they’re laying side by side.

As a show of gratitude, Sans nuzzles his face to Grillby’s and even adds some tongue in when the elemental responds favorably. But he stops after only a few seconds.

“ _hot_ damn, i’m outta fucks.”

_"please.... refrain from punning in my bed."_

“sorry, hot stuff.”

_“... sans... “_

Sans manages to scrap together enough energy for a small snicker. “what? don’t like the nickname? guess i could just call ya daddy.”

Grillby huffs and wraps his arms around Sans’ middle, turning him to spoon. He runs his hands across the cloth-covered stomach. 

_“ don’t make it weird… before the kid is born… ”_

“papa, then?”

“ _shut up and go to sleep, slut._ ”

“sure thing, papa. wait. that kinda sounds too much like papyrus. what else? father? nah, that’s too formal...”

Grillby groans. Sans grins. 

He’s happy.

**Notes for the Chapter:**

> hnnnn this is way longer than i was planning and technically i had to DOWNSIZE it already so. but i love sansby! and i love underfell! and so this was born. (and yes that was a hamilton reference if you saw it lol,, no need to point it out)
> 
> i'm still new to writing this ship so apologies if it's janky... im... doin my best...


	2. little star

Sans awakens to the feeling of hands on him. Warm hands. Grillby’s hands.

It’s not unusual, since Grillby often wakes up long before Sans on a regular day. He has a bar to run and all that.

What _is_ unusual is that Sans is up early enough to enjoy Grillby’s warmth next to him in bed. Sans gets up hours later than Grillby has the bar open on a good day, and is liable to sleep right until noon with nobody there to bang pots and pans until he does eventually snort awake.

Papyrus had always been the one to do that, but on the days Sans stays in with his _boyfriend_ , Sans doesn’t had an alarm clock of a brother to bother him. 

It means he’s always late to his station, if he even bothers showing up, but since his middle’s been growing, Papyrus has been pretty lenient about Sans’ hours. And no one bothers Paps about it due to the fact that he runs the Snowdin unit of the royal guard, which is an advantage Sans hadn’t ever thought he’d be using in the way he is now.

Nepotism is great.

The hand on Sans’ hip gives a little squeeze, and his conscious thought drifts back to the present moment, with Grillby practically coping a feel under the assumption Sans is asleep. He’d snicker and make fun of the elemental, but he's still tired and Grillby’s warm hands always feel nice.

Grillby’s other hand is rubbing circles into the false flesh of Sans’ middle. There’s still no SOUL, but it’s looking like there might be one very soon. The magic hasn’t dissipated, instead growing with every meal Sans eats and uh… every time he and Grillby enjoy some private time.

If Sans was any other type of monster, he might just attribute it to weight gain, but for skeletons, it’s a pretty set deal. His body is preparing to nurture a little SOUL.

And isn’t that just a novelty?

Sans had known what it meant, three or so months ago when he couldn’t consciously dispel his ecto-flesh. But he hadn’t known what it had _meant._

Even now, he goes about most of his day without thinking of the excess magic other than a complaint about his feet or his back or a brief rub to his stomach, right over where his navel would be, right a SOUL would eventually reside.

Hopefully.

Because Sans couldn’t be too sure right now, couldn’t be too optimistic.

Whenever Sans finds his thoughts drifting to his middle, he swiftly turns the topic to what he’ll be eating for lunch, or for dinner, or what Papyrus is doing or whether or not he thinks Red Bird and Bonnie are fucking on the side.

But… right now, being held by Grillby, in a warm bed…

Sans can let himself think about it. He can think about what it would be like to see a tiny SOUL, growing each day. He can think about how much _more_ his back will fucking hurt, how many pity massages he can coax out of Grillby when the time comes.

He lets himself think about watching a babybones grow inside of him. Tiny, tiny bones. Little sockets. Even smaller teeth.

Would they be sharp, like his? Or would they be duller, like he somewhat remembers Gaster’s being…

Would their magic be red? Or would it be purple, like Grillby’s? Would they even _be_ a skeleton?

What… what would it be like to hold them? 

To hear them cry and babble and feel them cling to him with tiny hands, clinging to the only semblance of warmth or care they’d likely receive Underground…

But there’d be Grillby for them, too. 

They wouldn’t be all alone, with only a sorry sack of bones to look out for them. They’d have two parents and an uncle and a nice warm house above a bar that had _plenty_ of food. It would be… It would be nothing like how Papyrus grew up.

And that certainly gives Sans _feelings_ , now doesn’t it?

There’s definitely a bit of nostalgia for the old days stuck in his bones, back when it was just him and Pap and Papyrus still looked up at him, was still _able_ to look up to him. Back then, it was a struggle everyday. 

Now, Sans can look ahead, has the _ability_ to look ahead because he knows the day is already handled.

And it’s different.

Maybe it’s better now, maybe Sans will always look back on his childhood and wish he could go back, if only to change a few things. Maybe there will always be things he wishes he got to do, got to experience just one more time.

But he’d take just one more morning waking up like this, safe and warm and with so much more hope than he ever thought possible, than a thousand more days sitting around a makeshift fire in Waterfall, eating what he could scrounge up after a day at the dump.

Sans _likes_ his life now. He wants it.

He _wants_ to have a baby with Grillby and spend the rest of his stupid life with him, taking care of whatever little thing comes from this. He wants to spend his nights at the bar and his mornings above it.

It almost _hurts_ , how much Sans wants.

And it’s too much when he feels more than hears Grillby sigh right next to his skull, warm breath on his vertebrae and warmer hands tugging him close to the taller monster.

There’s a burning heat behind Sans’ closed sockets, the feeling of magic wanting to escape. 

_Bitching stars,_ he’s crying. Fuck.

He wants to laugh at the same time, wants to turn around and kiss Grillby until his brain’s all stupid. Or, well, stupider than it already is.

Sans drags in an unsteady breath. It makes Grillby pause behind him, hands stilling in their gentle movements. But all Sans can think is that Grillby is _such_ a fucking freak if he touches up on Sans like this every morning before he wakes up.

The most infuriating, dumb, _wonderful, generous_ fucking _freak_ to ever exist Underground.

“ _... sans?”_

The hand on Sans’ hip slips up to his arm, and Sans shrugs it off so he can sit up. Grillby is already half-up next to Sans, trying to ask what’s wrong, but Sans just needs some _space_ so he can think about things without Grillby there to make his thoughts get all mushy and sappy again.

“bathr’m." Sans mumbles hurriedly before he slips out of bed and pads his way over to his destination. 

It’s a little bit of a ridiculous thing, seeing as neither he nor Grillby use the toilet and the shower is only there for if Sans needs to use it, which he almost never _does_ , but he closes himself in that little room and takes a few deep breaths.

The little pricks of tears at the corner of his eye sockets fall down his cheek bones, and Sans wipes them up with his arm. He’s in a sweater. Only a sweater, since despite the chill of Snowdin, Grillby gets _hot_ at night. Both figuratively and literally.

Also, pants are a fucking curse to society and Sans tries to get out of wearing them as often as he can.

For a moment, Sans takes deep breaths and wipes at his face until he’s absolutely _sure_ that it’s dry. When he takes a glance up at the permanently cloudy mirror, his SOUL almost stops.

… Sans doesn’t look in the mirror often.

He’s nothing much to look at, never has been. In his opinion, it’s his personality that’s gotten him by, and not even really that much. Most of it is probably due to his scrappiness, his ability to talk his way around a deal.

Sans will never know what he did to talk his way into Grillby’s bed, especially not after racking up such a high tab, but he’s never been one to look a gift horse in the mouth. Whatever the fuck that’s supposed to mean.

All he knows is that he’s been pretty damn lucky for basically his entire life, even when he was knocking on death’s door.

But when he looks into the mirror, he doesn’t feel the urge to look away or grimace. He’s a little frozen, staring at his own face.

Sans doesn’t think he looks any better than he usually does, and he definitely doesn’t look any worse, but it’s… strange.

It feels like… despite everything, it’s still him.

Stars, when’s the last time he’d looked at _him_? Sharp teeth, cracks and chips and red magic.

And it’s strange. To look at himself and to know that there’s nowhere else he’d rather be, no _one_ else he’d rather be.

He’s just Sans. And that’s fine.

Sans observes his reflection for a few more minutes, from the top of his skull to where the mirror cuts off at about his midsection. The red glow of his magic is visible even underneath his heavy sweater, especially in the dim lighting of the bathroom.

He fiddles with the hem of the sweater before pulling it up to his rib cage, just to take a little look at whatever progress is happening.

… It takes a second.

Okay, more than a second. More like a few seconds and some squinting, but Sans is sure that he sees something that doesn’t quite blend with the rest of his magic or the dull outline of the bone he can still sorta see underneath his false flesh.

It looks like a star. Or the imitation of a star, one that you’d find in the rocky ceiling of an underground cavern.

It’s nothing like the ones in Waterfall, where you can make out constellations if you’ve got enough time on your hands and food in your stomach, but there are rocks in other places. The ones in Snowdin are small and bright and they take a lot of staring to see. Just like the little spark of light in Sans’ middle.

A little star.

… 

Sans feels like his legs might give out under him.

By some miracle, they don’t, but it’s a near thing. He grasps the edge of the sink as close as he can without knocking his middle and stares a bit more. Sans twists a little, to see if it’s visible from more than one angle and barks out a sharp laugh when it moves along with him, fluttering and buzzing about in the magic that Sans’ body had been saving for so long now.

_stars._

_fuck._

Sans doesn’t know what to do besides laugh some more and bring a shaking hand up to his stomach and stroke over the flesh. He swears he can feel a spark from inside, a little ‘ _hi!_ ’ from the star within.

This is…

Sans barely knows what he should be feeling right now, but he knows what he _wants_ , and he wants to be back in Grillby’s arms.

So that’s what he does. 

Sans stumbles out of the bathroom, and back onto Grillby’s bed, _his_ bed, _their_ bed. He quickly climbs on top of the fire elemental, who had been sitting with his back to the headboard, and straddles him.

He’s grinning like a lunatic, probably looking absolutely manic as he leans in to press a bruising kiss against Grillby’s mouth.

Grillby’s hands come up to stabilize Sans at the hips as he leans away from the sudden onslaught of affection. “... _what’s gotten into you?_ ” He chuckles as Sans continues to try and pepper his face with little kisses.

“fuck you.” Sans tells him before pulling Grillby’s entire face to his and bringing their heads together so suddenly that there’s definitely a healthy dose of pain that results from the contact. “you fucking bastard.”

Grillby can’t even get a word in before Sans’ hips find his own and he grinds down viciously on his taller lover. Sans continues the violent make out session, insulting Grillby between kisses with various curses.

“you’re a fucking idiot.” Is apparently where Grillby draws the line.

He pries Sans’ face off of his own and holds him by his shoulders to keep him in place. They stare at each other for a bit, Sans’ face flushed and his grin not having moved an inch as he pants.

Grillby’s only a little better, still gasping a little for air and from surprise.

“... _what the fuck._ ”

“god, i hate you.” Sans laughs. He doesn’t go in for another kiss, though. Instead, he pulls his shirt up to his ribs and lets Grillby see. “you knocked me up, pinhead.”

Grillby’s gaze shoots down to Sans’ middle, and the skeleton can pinpoint the exact moment when he sees the little star for the first time. His hands shakily move from Sans’ shoulders to his stomach. His fingers stroke over the spot where the light is visible so softly Sans would wonder if it was happening at all, had he not been watching.

“... _i’m a fucking idiot._ ” Grillby says, finally.

Sans laughs and buries his face in Grillby’s chest.

“the worst.” He confirms.

“..... _we’re parents.”_ The words seem to shudder of out Grillby, disbelief heavy in his voice. 

Sans moves his hips again, and nuzzles into Grillby’s neck and nipping lightly. This time, Grillby moves back, and Sans can feel him getting _excited_ from his spot on Grillby’s lap. He’s a little excited, too, but at once something flashes through his mind and he freezes.

“... _?_ ” Grillby makes a questioning sound, but Sans is already sliding out of his lap to run over to where his jacket is strewn on the floor. He sits himself down and rummages until he pulls out his ancient flip phone.

“i gotta tell paps!”  
  


Grillby has enough humor left in him to chuckle and watch as Sans excitedly chatters into the phone, displaying more energy all at once than he had in the past year.

  
It’s not long until there’s the sound of heavy knocking on the door, a very distinct _Papyrus_ thing, and Sans is rushing down the stairs to greet him, still _sans_ of pants. Grillby doubts either of them will notice for a while.

**Notes for the Chapter:**

> this is for nanenna,,,,,
> 
> they is havin' a baby u//w//u!!!


	3. big worries

**Summary for the Chapter:**

> some snapshots as the pregnancy progresses *sparkles*
> 
> from grillby's perspective

After the little spark formed, the pregnancy pretty much snowballed. _Snowballed_. Sans would like that one, Grillby thinks.

During the months leading up to the formation of the souling, Sans hadn’t talked about his condition much at all. It was rare to see him even acknowledge it besides a few rubs to the stomach or some whining that lead to Grillby offering him some more massages or cuddles. A few times, Sans had used it as an excuse to get Grillby to cook for him.

Although, Grillby never needed any persuasion. Food is how he expresses himself, so it’s no surprise it’s also how he shows his love.

_Love._

That little word so often skirted around. Grillby lets Sans dance around it because he’s seen Sans’ soul, felt it, and that’s enough.

But the little star sitting in Sans’ middle changed all of that.

… 

The very next day, Sans sat at the bar as he usually does during the bar’s open hours. It’s more often than it used to be since he works less. But Sans has always been somewhat of a fixture at his restaurant, so the regulars pay no mind and the monsters from out of town keep to themselves.

When noon rolled around, Grillby disappeared into the back for only a minute to get out some fries as he usually does. Stopping by the pantry, he grabbed a fresh bottle of mustard and strode out to the bar. Without a word or a look, he set them down in front of Sans and went back to his usual business.

And per _usual,_ Sans happily made a puddle of mustard on his plate, only to dunk three or so fries in before taking a big bite.

Grillby is careful to angle his face away, to appear disinterested, but the sunglasses he wears hide the way his gaze is fixed straight on Sans’ face. It’s something he’s not sure if Sans is aware of, but Grillby is obsessed with him in the way lovers are.

Maybe it’s obvious to the little skeleton with a sharp smile and a sharper eye, but he’s never commented on Grillby’s habit.

He likes to know that he’s taken care of his own, and the way Sans lights up when he tastes what Grillby’s made is deeply satisfying.

… 

That day, he found none of that brightness on Sans’ face when he started chewing. Instead, he got a front row seat to the way sweat beaded on his lover’s skull and his eye lights shrunk. To the way his shoulders slumped and he chewed so _slowly_.

Grillby got to watch as Sans reluctantly swallowed the oversized bite he’d taken and slowly, shamefully, slid off of his stool at the bar. 

He still thanks the stars above that nobody had noticed the way Sans scurried behind the bar and past the fire exit, likely to run upstairs. 

At a complete loss, Grillby set down the glass he’d been polishing and told everybody in the bar to _get out_. It wouldn’t be the first time he shut the bar down suddenly, but it had usually been due to more pressing circumstances.

But as he chased loyal patrons and random monsters out, he didn’t have business or money on his mind. Only the way Sans had pushed his plate away before dashing away, looking absolutely mortified. 

Grillby knows Sans doesn't like to be emotional in public. It’s almost social suicide, which could lead to very real dangers if he’s caught alone with someone who cares more for exp than Sans’ at times snarky attitude. Grillby himself has gotten quite annoyed with Sans, but he’s ultimately not that type of monster.

(He’s glad, now, thinking on how he waited for years before approaching Sans, before realizing that the mild interest had been the start of so much more.)

And pregnant monsters are so vulnerable. Just realizing that, while telling his customers to scram, Grillby had the disturbing and strong thought to keep Sans locked away in his apartment for the pregnancy, until he was strong again. Perhaps even after that, keep him up there with their kid until they weren’t so small anymore.

The temperature in the bar must have risen by at least five degrees, which finally convinced the last few stubborn monsters to clear out, leaving behind their food. Grillby locked the door behind them, shut the windows and barred them, before rushing right upstairs to Sans.

… Grillby heard him before he saw him. A sound so rare, Sans’ harsh and uneven breathing that usually betrayed tears.

All at once, that heat fled Grillby, his flames burning low as he slowly approached the bedroom and knocked before shuffling inside.

There, on the bed, was Sans. He had pulled all of the blankets around him until he resembled a cocoon and was sniffling into Grillby’s pillow. Just as slowly as before, Grillby approached the bed before sitting and pulling Sans into his lap.

For a moment, Sans pushed Grillby away with stuttered protests before eventually collapsing into him. He hid his face in Grillby’s shoulder, still refusing to show the tears Grillby could feel soaking into his shirt. They sizzled gently against him, creating steam that condensed on Sans’ skull and dripped down his vertebrae.

Eventually Sans was calm enough to talk. 

The first thing Grillby wanted to know was if he had somehow burnt the fries, or seasoned them wrong, or if they were somehow subpar. His voice felt thick as he asked, remembering the way Sans’ entire demeanor had crumpled as soon as he’d sampled some of Grillby’s fries.

It stung more than magical tears ever would.

But Sans told him, through sniffles, that the food tasted the same. It had just suddenly and inexplicably become unbearable for him to eat. Disgusting, even. Grillby felt utterly crestfallen, flames dropping even lower. 

Despite feeling rather disappointed and guilty himself, he comforted Sans some more, then offered to make him something else. Grillby almost felt desperate when he offered, wanting to prove to himself and Sans that he was still a good provider.

And thus started the most painful few hours of Grillby’s career since he’d almost lost the bar fifty years or so ago.

Dish after dish, from burgers to mac ‘n cheese, Sans took one bite only to spit it out directly after.

It would be a lie to say that Grillby’s pride wasn’t wounded. Monsters came out all the way from New Home to try his food, and they paid good gold for it, too. He’s always been confident in his ability to cook.

And yet, Sans hated everything he made. 

After the fifth dish Grillby didn’t have any more ingredients to work with and they had to stop, so Sans sat despondently with a few bananas to eat for lunch. Grillby watched as he sniffled through bites, wiping his sockets every few seconds to erase the evidence of his weakness.

With so much food Sans refused to eat, Grillby was forced to call Papyrus, hoping that the guard could take the extra off of his hands. Later that evening, when Papyrus dropped by, Sans clung to him and demanded more than asked for lasagna.

Papyrus tried his best to look offended at the order, but was ultimately happy to see his brother scarf serving after serving down when he brought it by ten or so minutes later.

For the following months, Sans ate almost exclusively ate some type of pasta or noodle, all of which Papyrus was happy to experiment with. 

Grillby watched jealously and anxiously as Papyrus eventually brought more of his things over to _his_ kitchen, setting up like it was his own space while Sans waited eagerly at the small table for dinner. And Papyrus made dinner for them _every night_ , packing up leftovers for Sans to have for lunch the next day.

For breakfast, Sans gained a new interest in fruit. Grapes, strawberries, orange juice. He’d never been overly fond of sweet things before, but for a month the Underground had a shortage of strawberries due to an infestation of slugs in Waterfall and Sans had cried nearly every morning without them.

Beyond his sudden hatred for Grillby’s food, Sans gained a few more eating quirks even odder than his love for mustard.

Suffice to say, Grillby once walked in on Sans quickly making himself a bowl of Papyrus’ lasagna with the hardly used horseradish sauce. Just as fast, Sans had dropped the bottle of condiment and fled into the room, taking his lasagna with him.

Grillby said nothing of it, but ordered a whole new shipment of the spicy condiment, which was quickly assimilated into their personal pantry.

* * *

It had definitely been a rough few months, especially for Sans. Grillby felt the effects, though. He’s comforted Sans through crying fits, been a pillow for punching when Sans is irritable and a hand to hold during those times Sans craves closeness.

… It definitely doesn’t hurt that he’s just as excited for their child as Sans is. Every morning and every night, Grillby laid curled around Sans in their bed. He slipped his hands up underneath Sans’ baggy shirt and stroked the ecto that has become larger and tighter around his midsection, feeling out the warm spot where the souling is closest to the surface.

Unfortunately, the flesh had eventually clouded over as the body started to form, meaning that they couldn’t see the baby anymore. It could still be felt, though, like little sparks of electricity when it fluttered.

Grillby often stayed up for maybe an hour after Sans fell asleep every night, just stroking over his stomach and murmuring softly. He wanted their child to recognize him as soon as they're born. Wanted to be the type of father he’d never had, who will stick by his family through the good and the rain.

As he fell asleep each of those nights, he imagined carrying them in his arms. Imagined Sans smiling at him with all the warmth of a thousand suns, of a _soulmate_ , true and lovely.

And he thinks that perhaps they really do have this, after all. That they can take on the Underground and the world alike.

* * *

That confidence flickers out in one moment near the end of Sans’ pregnancy.

At that point, Sans was so round he waddled instead of walking and had to sit down more often than before. Which was significant taking into account that it was _Sans_ they were talking about.

Strangely, Sans became incredibly stubborn about resting. His bullheadedness had turned to insisting that he could care for himself, that he was capable, and yet, he was often bent over some surface heaving for breath.

Not even Papyrus had been able to force him into maternity leave. The time he’d tried, Sans had stubbornly waded through snow up to his hips and sat at his sentry station for a whole hour before Grillby realized he was missing and went out to fetch him.

Sans complained the whole way back, but obviously clung to Grillby to warmth as his bones chattered. For the rest of the day he agreed to sit in bed and nibble at a bowl of pho.

That event had scared Grillby, but it was nothing like the time he’d been working at the bar and heard a thump followed by a shatter upstairs. After that, silence.

It had been so loud that every single monster in the bar had heard it, and had frozen.

… They didn’t need encouragement beyond Grillby telling them to get out, that time, before emptying the bar. Grillby didn’t even lock the bar down before rushing upstairs, scenario after scenario running through his head about what could have happened.

Sans could have fallen, could have broken something and passed out, or….

It was terrifying, not knowing. His flames burnt so hot that he scorched the door to the apartment as he burst in.

… Only to find Sans sitting on the ground in the kitchen, breathing heavily, with a glass jar of pickles broken a foot in front of him, the contents spilled out across the ground. A step ladder was beneath an open cabinet on its side.

“... i tripped.” Was all he had to say before Grillby was all over him.

First, the fretting. Checking Sans all over to make sure he hadn’t sustained any injuries while Sans begrudgingly let him. The entire time, the small skeleton protested, but his body was limp as Grillby checked over every inch of his bones.

Next, the fear. Realizing for not the first time that Sans could so easily be taken away from him, with only 1 hp. Realizing that he could take their baby with them, and Grillby would be left alone. It wasn’t the first time Grillby’s thoughts had traveled down that path, but it was definitely the most intense. The baby was so close to being born, it was more real now than ever.

Lastly, and mostly as a consequence of the fear, Grillby got angry. So, _so_ angry.

It was irrational, looking back. But it had burned through him as sure as the fire he was made of and he had yelled at Sans for being careless. Clumsy. Accused him of not caring properly for the child he was carrying.

Understandably, Sans got upset. He started to yell back, tears quickly dripping down his face. They argued for all of half an hour before Sans locked himself in the bathroom and called Papyrus to pick him up.

Sans stayed with his brother for a week after that.

It gave Grillby time to think.

Sans could have died when he tripped. It would have only taken one wrong move before the skeleton was little more than dust dissolved in pickle juice and Grillby couldn’t stand the idea of it. If he hadn’t heard the thump, he would have never known anything was amiss at all. If Sans was out, and fell, or was attacked, Grillby would be none the wiser until he didn’t show up at home.

The dust would be gone in the wind.

… The spot in the bed that Sans usually occupied had never felt so cold or empty.

And Grillby, who had always been a decisive sort of monster, decided to do something about it. The next day, he locked his bar down (which was becoming increasingly common) and trekked all the way out to the Capital to hunt in the shops for something.

He and Sans had discussed bonding. They knew it was serious business, and while Grillby was ready after centuries thinking he would be alone until he burnt out, Sans was still unsure. Grillby promised to wait, and that night, he and Sans enjoyed nothing more than gentle kisses which were quite unusual in themself.

But Grillby’s patience had been tested by the incident. He needed to know that Sans was safe, that there would be a tie to keep his small lover close to his soul no matter where they were.

So.

With a pouch of gold, Grillby searched high and low for an offering to hopefully convince Sans the commitment would be worth it.

… He settled for a simple collar, so unlike the one Sans wore as a sentry. It was soft, jet black, and thin. It would fit just loose enough to allow Sans comfort while he wore it, and it was perfect.

Grillby bought it and returned back to his bar, trying not to let his flame flicker too much as to betray emotion.

* * *

When Sans returns, Grillby hugs him and apologizes. 

Sans allows the contact. He nuzzles into Grillby’s shoulder and sighs. “shuddup already.” He grouses softly, arms winding their way around Grillby’s shoulder. “i was actin’ fucking stupid.”

“... _i shouldn’t have said what i did_...“ Grillby insists. He takes a minute to just feel _Sans_ in his arms, alive, sturdy as he’s always been. He has to partially squat to make his face level with the skeleton’s, but he pays it no mind.

“didn’t say nothing that wasn’t true.” Sans tells him. “even if you were bein’ a fuckin’ asshole about it. i was... i wasn' being careful. if i had... if i had..” He trails into something quiet and pained

Grillby doesn’t say it out loud, but he missed Sans’ vulgar language like a bird with clipped wings misses flying. He holds Sans tighter. ".... _you wouldn't have... let that happen..._ "

Sans chuckles and pats Grillby on the back indulgently. “alright, alright, papa. you’re gonna squish the baby.”

The elemental sits back, if only to check on the swell of Sans’ middle. He rubs his hands over it, feeling the cold magical flesh. Immediately, he gets to work warming his hands and trying to take away the chill of Snowdin.

Sans sighs and pats over Grillby’s hands. “they missed ya.” He hums. “felt ‘em kicking up a damn storm every single night.”

Grillby feels the flames of his face split in a wide grin, sure that his effort hasn’t gone to waste.

“heheh, don’t look so damn happy wit’ yerself.” Sans chides lightly, “i’m tired and pap doesn’t give foot rubs.”

* * *

… Grillby makes sure everything is perfect.

Sans changes into one of Grillby’s larger and softer shirts, one that will cover his belly and his thighs, relaxing into the bed as his boyfriend lavishes him with attention. He sighs and coos when Grillby kisses him, murmuring rare praise speckled with more apologies that light Grillby up like nothing else.

Their bedroom is lit with only the light of his flames, which cast a brilliant glow on Sans’ bones. When Grillby shifts to sit against the headboard and drag Sans into his lap, the skeleton lets him push the shirt up until his middle is showing. 

Grillby takes turns kneading Sans’ shoulders and rubbing at his middle lightly.

As Grillby moves his hand down to start stroking at Sans’ false flesh again, the skeleton catches it and holds it to his face. He sighs and nuzzles into the fire.

“stars, yer the fuckin’ best.” Sans groans. “i could just… fuckin’... marry ya or somethin’.”

… They both freeze at the same time.

Sans, likely out of fear at his admission.

Grillby, because he suddenly remembers the collar still stashed away in the drawer of his nightstand.

“... fuck…” Sans gasps quietly to himself, covering his face in shame.

Grillby fumbles to try and find the collar with one hand while holding Sans tightly to himself. His soul is racing, soaring, somewhere on the surface with how high he feels.

He’s never been the best with words. Somehow Sans draws them out of him, though. With word play or snark that Grillby finds an easy rhythm with. Now, though, he can’t find the words as he finally grasps the collar and holds it in front of Sans.

_“... care to put your money… where your mouth is..?”_ He finally says.

Slowly, Sans lowers his hands from his face. Grillby wishes he could see the smaller’s expression, but he’s forced to wait as Sans processes.

...

“i..” Sans starts, only to pause for another minute. “i ain’t given you a single fuckin’ g in three years.”

Grillby’s flames crackle in slight amusement.

“... _and a half… is that a no? "_

The small skeleton breaks free of Grillby’s hold and turns to face him head on. “you’ve got…” There’s small tears beading at the corner of his sockets. “you’ve got half a fuckin’ _brain_ if you think imma say no!”

Sans snatches the collar and looks at it closely. He looks as though he’s scrutinizing it, but he quickly starts to put the thing on. Grillby helps and Sans doesn’t push him away.

It’s no soul bond, not by a long shot.

But soon.

And that’s all Grillby can ask for.

**Notes for the Chapter:**

> is underfell sansby quickly becoming one of my all time favorites? hm.
> 
> anyways i love them a whole bunch

**Author's Note:**

> anyways i hope you're all doing well! remember to stay safe and all that jazz!! leave a comment if you wanna chat or smth andddddd [here](https://beanniebenn.tumblr.com/) is my tumblr.


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